Displays in image display devices, such as television devices, are now being shifted from conventional cathode-ray tube displays to thin displays, such as liquid crystal displays and plasma displays. With the thin displays, the thicknesses of the image display devices can be decreased. Liquid crystal panels included in the liquid crystal display devices do not emit light, and thus backlight devices are required as separate lighting devices.
An edge light-type backlight device including a light guide plate with a light entrance surface on the side and light sources such as LEDs arranged closer to the side of the light guide plate is known as an example of a backlight device. In such a backlight device, a reflection sheet may be placed on surface of a bottom plate of a chassis and the light guide plate may be placed on the surface of a reflections sheet (as in a backlight device disclosed in Patent Document 1). Because the light guide plate is placed on the surface of the reflection sheet, no gap is provided between the reflection sheet and the light guide plate. Therefore, a loss in reflection light between the reflection sheet and the light guide plate is reduced or suppressed.